scanner.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Tue Jun 23 12:18:41 2020

@author: edoardottt
"""

import socket

import threading
import time
import os
import struct
from netaddr import IPNetwork, IPAddress
from ctypes import *

# host to listen on
host = "192.168.0.180"

# subnet to target
subnet = "192.168.0.0/24"

# magic string we'll check ICMP responses for
magic_message = "PYTHONRULES!"

# this sprays out the UDP datagram
def udp_sender(subnet, magic_message):
    time.sleep(5)
    sender = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    for ip in IPNetwork(subnet):

        try:
            sender.sendto(magic_message, ("{}".format(ip, 65212)))
        except:
            pass


# our IP header
class IP(Structure):
    _fields_ = [
        ("ihl", c_ubyte, 4),
        ("version", c_ubyte, 4),
        ("tos", c_ubyte),
        ("len", c_ushort),
        ("id", c_ushort),
        ("offset", c_ushort),
        ("ttl", c_ubyte),
        ("protocol_num", c_ubyte),
        ("sum", c_ushort),
        ("src", c_uint32),
        ("dst", c_uint32),
    ]

    def __new__(self, socket_buffer=None):
        return self.from_buffer_copy(socket_buffer)

    def __init__(self, socket_buffer=None):

        # map protocol constants to their names
        self.protocol_map = {1: "ICMP", 6: "TCP", 17: "UDP"}

        # human readable IP adresses
        self.src_address = socket.inet_ntoa(struct.pack("@I", self.src))
        self.dst_address = socket.inet_ntoa(struct.pack("@I", self.dst))

        # human readable protocol
        try:
            self.protocol = self.protocol_map[self.protocol_num]
        except:
            self.protocol = str(self.protocol_num)


# our ICMP header
class ICMP(Structure):

    _fields_ = [
        ("type", c_ubyte),
        ("code", c_ubyte),
        ("checksum", c_ushort),
        ("unused", c_ushort),
        ("next_hop_mtu", c_ushort),
    ]

    def __new__(self, socket_buffer):
        return self.from_buffer_copy(socket_buffer)

    def __init(self, socket_buffer):
        pass


# check the OS
if os.name == "nt":
    socket_protocol = socket.IPPROTO_IP
else:
    socket_protocol = socket.IPPROTO_ICMP

sniffer = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket_protocol)

sniffer.bind((host, 0))
sniffer.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)

if os.name == "nt":
    sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)

# start threading packets
t = threading.Thread(target=upd_sender, args=(subnet, magic_message))
t.start()

try:
    while True:

        # read in a packet
        raw_buffer = sniffer.recvfrom(65565)[0]

        # create an IP header from the first 20 bytes of the buffer
        ip_header = IP(raw_buffer[:20])

        # print out the protocol that was detected and the hosts
        print(
            "Protocol {} {} -> {}".format(
                ip_header.protocol, ip_header.src_address, ip_header.dst_address
            )
        )

        # if it's ICMP, we want it
        if ip_header.protocol == "ICMP":

            # calculate where our ICMP packet starts
            offset = ip_header.ihl * 4
            buf = raw_buffer[offset : offset + sizeof(ICMP)]

            # create a new ICMP structure
            icmp_header = ICMP(buf)

            print(
                "ICMP -> Type: {} Code: {}".format(icmp_header.type, icmp_header.code)
            )

            if icmp_header.code == 3 and icmp_header.type == 3:

                # make sure host is our target subnet
                if IPAddress(ip_header.src_address) in IPNetwork(subnet):

                    # make sure it has our magic message
                    if (
                        raw_buffer[len(raw_buffer) - len(magic_message) :]
                        == magic_message
                    ):
                        print("Host Up: {}".format(ip_header.src_address))

# handle CTRL + C
except KeyboardInterrupt:

    # if we're using Windows, turn off promiscuous mode
    if os.name == "nt":
        sniffer.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)